It is well known that certain human disease states respond favorably to the treatment of certain blood components by visible or ultraviolet irradiation, with or without the introduction of outside agents, compounds or catalysts. For example, it is known that psoralen compounds form photoadducts with DNA in the presence of ultraviolet radiation, thereby moderating the viability of leukocyte populations.
Systems employing these techniques are known whereby extracorporeal treatment of a patient's blood is undertaken. For example, in U.S. Pat. No. 4,573,960--Goss, a patient is given a drug that requires photoactivation and the patient's blood is then withdrawn and separated into its components. The undesired components are returned to the patient. The patient is then disconnected from the treatment apparatus and the separated components, e.g., white blood cells, are exposed to ultraviolet light. Following photoactivation, the treated cells are returned to the patient.
In prior art systems such as those described in the Goss patent, the actual separation of white blood cells from whole blood requires subjective judgement on the part of the operator of a centrifuge, and inevitably results in contamination with some red blood cells. The contamination interferes with the irradiation process and reduces the effectiveness of the treatment. This problem has been largely solved by the methods and apparatus disclosed in U.S. Pat. No. 4,921,473--Lee et al., which is assigned to the assignee of the present invention and is incorporated herein by reference. In the apparatus disclosed in the Lee et al. patent, the fluid to be irradiated is introduced into a sealed chamber. The rotation of the chamber centrifugally separates the fluid into layers and the inner layer or layers are exposed to a light source disposed opposite a transparent inner wall of the chamber. The chamber then ceases rotating, remixing the components of the fluid, and the reconstituted fluid is returned to the patient.
However, although the apparatus disclosed in the Lee et al. patent provides greatly enhanced results, a number of problems exist which, if overcome, would further enhance the effectiveness and efficiency of such systems. It would be desirable, for example, to provide an ultraviolet lamp configuration that provides the highest radiation density against a spinning cylindrical wall. Because the photoactivation treatment should be controlled and repeatable such a lamp configuration should be designed so that it cannot be used after the performance of the lamps has degraded below a certain level. Additionally, because it is necessary to place the lamp assembly within the center of a spinning centrifuge chamber, space is at a premium and the lamp assembly should occupy a minimum envelope and also be able to accommodate variations in bulb dimensions so that conventional commercially available bulbs can be used. Although ultraviolet bulbs are available in standard sizes, the dimensional tolerances are not tightly controlled thus any configuration for retaining standard bulbs in an array must accommodate the dimensional variations in the replacement bulbs.
It would also be desirable to be able to replace the lamp assembly quickly and easily to minimize down time after the lamp assembly has degraded and must be replaced. Conversely, the lamp assembly should be integrated into the equipment so that other normally replaced or renewed components can also be maintained without having to remove the lamp assembly. For example, in certain embodiments of photoactivation equipment it is necessary to replace a disposable irradiation chamber and blood tubing. It would be desirable to be able to undertake such replacement without disconnecting the lamp assembly. Moreover, in certain equipment, it is necessary that tubing carrying the whole blood occupy space within the centrifuge chamber such that the light array could interfere with the tubing as the chamber is opened and closed. Clearly, such interference should be avoided and the structure of the apparatus should protect the blood tubing where possible. Finally, it would also be desirable of the lamp power and signal electronics were connected to the lamps without interfering with the rotation centrifuge chamber.